Resonant Raman scattering off neutral quantum dots

Resonant inelastic (Raman) light scattering off neutral GaAs quantum dots which contain a mean number, N=42, of electron-hole pairs is computed. We find Raman amplitudes corresponding to strongly collective final states (charge-density excitations) of similar magnitude as the amplitudes related to weakly collective or single-particle excitations. As a function of the incident laser frequency or the magnetic field, they are rapidly varying amplitudes. It is argued that strong Raman peaks should come out in the spin-density channels, not related to valence-band mixing effects in the intermediate states.Comment: Accepted in Physical Review

Spin polarization and magneto-luminescence of confined electron-hole systems

A BCS-like variational wave-function, which is exact in the infinite field limit, is used to study the interplay among Zeeman energies, lateral confinement and particle correlations induced by the Coulomb interactions in strongly pumped neutral quantum dots. Band mixing effects are partially incorporated by means of field-dependent masses and g-factors. The spin polarization and the magneto-luminescence are computed as functions of the number of electron-hole pairs present in the dot and the applied magnetic field.Comment: To appear in Phys. Rev.

The effects of normal and shear stress wave phasing on coseismic landslide displacement

Predictive models used to assess the magnitude of coseismic landslide strain accumulation in response to earthquake ground shaking typically consider slope-parallel ground accelerations only and ignore both the influence of coseismic slope-normal ground accelerations, and the phase relationship between dynamic slope-normal and slope-parallel accelerations. We present results of a laboratory study designed to assess the significance of the phase offset between slope-normal and slope-parallel cyclic stresses on the generation of coseismic landslide displacements. Using a dynamic back-pressured shearbox that is capable of simulating variably-phased slope-normal and slope-parallel dynamic loads, we subjected sediment samples to a range of dynamic loading scenarios indicative of earthquake-induced ground shaking. We detail the variations in strain accumulation observed when slope-normal and slope-parallel stresses occur independently and simultaneously, both in and out of phase, using a range of dynamic stress amplitudes. Our results show that the instantaneous phasing of dynamic stresses is critical in determining the amount of coseismic landslide displacement, which may vary by up to an order of magnitude based solely on wave phasing effects. Instantaneous strain rate is an exponential function of the distance normal to the Mohr Coulomb failure envelope in plots of shear stress against normal effective stress. This distance is strongly controlled by the phase offset between dynamic normal and shear stresses. Our results demonstrate that conditions considered by conventional coseismic slope stability models can either over- or under-estimate earthquake-induced landslide displacement by up to an order of magnitude. This has important implications for accurate assessment of coseismic landslide hazard

Estimation of lean body mass in children

BACKGROUND In adults, dosages of some anaesthetic agents are based on lean body mass (LBM) rather than body weight. Our aim was to derive an equation for estimating LBM in children. METHODS Patients comprised three groups: prospective kidney transplant donors from two separate centres (centres 1 and 3) and children referred to a further centre (centre 2) for the routine clinical measurement of glomerular filtration rate (GFR). GFR and extracellular fluid volume (ECV) were measured using Cr-51-EDTA. LBM was directly estimated (eLBM) in adults using an equation based on height and weight. ECV in children was estimated (eECV) from another equation based on height and weight, converted to eLBM using the relationship between eLBM and ECV determined in the adults from centre 1 and then compared with adult data from centre 3. RESULTS In children, the ratio of eECV to ECV was 1.04 (SD 0.18). In centre 1, eLBM (kg) was 3.81 (SD 0.55) times greater than ECV (litres) in men (n=50) and 3.77 (0.77) times greater in women (n=51). eLBM in children was therefore derived by multiplying eECV by 3.8. In children, eLBM showed a close linear correlation with measured ECV (eLBM=3.50ECV+2.0; R(2)=0.857), similar to adults (eLBM=2.82ECV+14.5; R(2)=0.582). In all groups, eLBM/weight correlated inversely with weight. CONCLUSIONS In terms of the relationships between eLBM, ECV, and weight, children are similar to adults. Therefore, drug dosage in children should also be based on eLBM rather than weigh

Estudio geológico de la Cordillera Occidental del Norte del Perú - [Boletín D 10]

El estudio analiza la geología de la Cordillera Occidental del Perú, desde la latitud cercana a Lima hasta la frontera con el Ecuador. Se evalúa la cadena montañosa comprendiendo rocas de edad mesozoica así como la parte occidental de la Cordillera Andina. El área de estudio se encuentra dentro de latitudes tropicales, con influencia de vientos alisios del Sureste y contexto árido (desde el nivel del mar hasta los 1500 m.s.n.m ) y con zoneamiento climático vertical (desde 2500 a 4500 m.s.n.m.) controlado por la altitud. Se analiza la geomorfología constatando las elevaciones concordantes y un patrón de drenaje maduro, observado por McLaughlin en la llamada Superficie Puna y la evaluación de las rocas volcánicas y sedimentarias. La estratigrafía revela la presencia del Mesozoico y Cenozoico en Los Andes Septentrionales y Centrales del Perú, detallándose los depósitos de las distintas formaciones. En cuanto a la geología estructural se identifican las diversas estructuras del sistema montañoso. Se calculan e interpretan las Edades radiométricas. Se aporta la geoquímica aplicable a las rocas intrusivas y volcánicas del Perú Central. Se realizó un mapeo de reconocimiento geológico y levantamiento geoquímico del Sector Norte de la Cordillera Occidental, evaluando el potencial minero y delineando depósitos desconocidos con importancia económica, en la provincia polimetálica andina (Norte de Chile y Bolivia hasta el Ecuador). El reconocimiento geoquímico abarcó un área de 25000 km², entre las latitudes 4° 30’ S y 7° 15’ S y longitudes 78° 0’ y 80° 0’. Se reporta la mineralización conocida en el área que incluye los depósitos de Michiquillay, Turmalina y el Distrito de Hualgayoc. Se destacan tres anomalías principales de las cuales dos exhiben cursos de dispersión geoquímica considerablemente más largas que Michiquillay. Esta investigación forma parte del Programa de Cooperación Técnica entre los gobiernos Británico y del Perú y los trabajos de campo y gabinete tuvieron desarrollo entre los años 1963 y 1972. Incluye bibliografía

Pertussis disease and antenatal vaccine effectiveness in Australian children

Background: Population-level studies of severe pertussis extending beyond infancy are sparse, and none in the context of antenatal vaccination. We compared hospitalized pertussis cases from birth to 15 years of age before and after introduction of antenatal immunization. Methods: Active surveillance of laboratory-confirmed pertussis hospitalizations in a national network of pediatric hospitals in Australia January 2012 to June 2019. Impact of maternal vaccination was assessed by vaccine effectiveness (VE) in cases and test-negative controls with <2 months of age and by before-after comparison of age distribution of cases. Among cases eligible for one or more vaccine doses, we examined proportions ageappropriately immunized and with comorbidities by age group. Results: Among 419 eligible cases, the proportion <2 months of age significantly decreased from 33.1% in 2012 to 2014 compared with 19.6% in 2016 to 2019 when mothers of only 4 of 17 (23.5%) cases <2 months of age had received antenatal vaccination. VE was estimated to be 84.3% (95% CI, 26.1–96.7). Across all years (2012–2019), of 55 cases 4–11 months of age, 21 (38%) had ≥2 vaccine doses, whereas among 155 cases ≥12 months of age, 122 (85.2%) had ≥3 vaccine doses. Prevalence of comorbidities (primarily cardiorespiratory) increased from 5 (2.1%) <6 months of age to 36 (24.2%) ≥12 months of age (P < 0.001), with 6/16 (38%) cases ≥12 months of age who required intensive care having comorbidities. Conclusions: Below the age of 12 months, prevention of severe pertussis will be maximized by high maternal antenatal vaccine uptake and timeliness of infant vaccine doses. Despite full immunization, we found children ≥12 months of age accounted for 27% of hospitalizations <15 years, with 24% having comorbities, suggesting new vaccine strategies, such as additional doses or more immunogenic vaccines, require evaluation.Helen E. Quinn, Jeannette L. Comeau, Helen S. Marshall, Elizabeth J. Elliott, Nigel W. Crawford, Christopher C. Blyth, Jennifer A. Kynaston, Tom L. Snelling, Peter C. Richmond, Joshua R. Francis, Kristine K. Macartney, Peter B. McIntyre, and Nicholas J. Woo

Whole-cell pertussis vaccination and decreased Risk of IgE-mediated food allergy: a nested case-control study

BACKGROUND:Rates of food allergy have increased markedly in Australia and other high- income countries in recent years. On the basis of ecological observations, and the known immunologic characteristics of whole-cell pertussis (wP) compared with acellular pertussis (aP) vaccines, we hypothesized that wP vaccination in infancy protects against the development of food allergy. OBJECTIVE:To determine whether infants who receive wP in infancy were less likely to develop IgE-mediated food allergy than those who received aP. METHODS:Retrospective cohort-nested case-control study of Australian children born in the period 1997 to 1999, the period of transition from using wP-containing to aP-containing vaccines. Children diagnosed with IgE-mediated food allergy were individually matched to 10 controls by date of birth, socioeconomic decile, and jurisdiction of birth. The odds ratio of vaccination with wP versus aP among cases and matched controls was calculated using conditional logistic regression. RESULTS:The odds ratio of receiving the first dose as wP (rather than aP) among cases of food allergy compared with controls was 0.77 (95% CI, 0.62-0.95). The results of secondary analyses (any dose as wP vs aP-only, and wP-only vs aP-only) were broadly similar. CONCLUSIONS:Australian infants who received wP vaccines were less likely to be diagnosed with food allergy in childhood than contemporaneous children who received aP vaccines. If a protective effect is confirmed in a randomized controlled trial, wP or mixed wP and aP vaccination schedules could form part of an effective strategy for combating the rise in food allergies.Marie J.Estcourt, Dianne E.Campbell, Michael S.Gold, Peter Richmond, Katrina J.Allen, Helen E.Quinn ... et al